Energy absorption device and passenger safety crossbar system incorporating same

ABSTRACT

An energy absorption device comprises an elongated base member ( 22 ) and an elongated mechanically fused spring arm ( 30 ) extending longitudinally from a first end ( 32 ) secured to the base member to a free distal end ( 34 ). The spring arm has resilience for storing mechanical energy when flexed from a normally unflexed position&#39; to a flexed position. During such movement, the resistance offered by the mechanical fusing must be overcome. Thus the device serves both to store and to dissipate mechanical energy. Suitable fusing mechanisms include shear pins and mechanical fuse strips ( 40 ). A system comprising a passenger safety crossbar ( 10 ) supported by a pair of such energy absorption devices is also disclosed.

FIELD OF THE INVENTION

The present invention relates to energy absorption devices and to asystem using same to protect vehicle passengers by absorbing crashenergy.

BACKGROUND TO THE INVENTION

In some vehicles, school buses being a particular example, safetydevices such as ordinary seat belts or shoulder harnesses may beconsidered unsuitable not only because they may become a source ofinjury if not used properly but also because some of the young occupantsmay be disinclined to use the devices in the intended manner or at all.

In view of such considerations, various restraint systems which includea safety bar adapted to extend across the lap of seated passengers havebeen proposed for buses. These include the safety bar system describedin U.S. Pat. No. 4,681,344 (Majerus) granted on Jul. 21, 1987, therestraint system described in U.S. Pat. No. 4,930,808 (Mikoll et al.)granted on Jun. 5, 1990, and the restraint apparatus described in U.S.Pat. No. 5,853,193 (Marshall) granted on Dec. 29, 1998. At least in thelatter two cases, the systems described have a degree of flexibility orgive beyond mere padding that serves to absorb the kinetic energy of apassenger who impacts the bar during a crash. But, if the amount offlexibility is designed with teenagers or adults in mind, the system maybe excessively rigid for a six year old sitting alone or even withanother six year old. Likewise, if the amount of flexibility is designedwith a six year old in mind, the system may be too flexible for ateenager or adult or two teenagers or adults sitting together.

Accordingly, there is a need for a passenger safety crossbar systemwhich can afford effective protection over a significant range ofpassenger weights. As well, there is a need for an energy absorptiondevice that can be adapted to support a passenger safety crossbar andserve to protectively absorb energy transmitted to the device from acrash impact on the crossbar either from a relatively light passenger orfrom relatively heavy passengers.

SUMMARY OF THE INVENTION

In a broad aspect of the present invention, there is provided an energyabsorption device comprising an elongated base member, an elongatedspring arm extending longitudinally from a first end secured to the basemember to a distal end, the arm having resilience for storing mechanicalenergy when flexed from a normally unflexed position to a flexedposition, and mechanical fuse means for providing fuse resistance to theflexing of the arm from the unflexed position to the flexed position.When the spring arm is in the unflexed position its distal end isrelatively near the base member. When the spring arm is in the flexedposition its distal end is relatively far from the base member.

Herein, the term “mechanical fuse” means an element which offers apredetermined amount of resistance (“fuse resistance”) to a mechanicalforce. When the resistance is overcome by a suitably high force, thefuse actuates by breaking or deforming in a destructive manner therebydissipating mechanical energy. Thus, when the spring arm is flexed fromthe unflexed position to the flexed position, energy is absorbed andmanaged in two different ways. Firstly, by virtue of the arm's springcharacteristic, mechanical energy is absorbed and stored in the arm.Secondly, since fuse resistance must be overcome in order to flex thearm from the unflexed position to the flexed position, mechanical energyis absorbed and dissipated by the mechanical fuse means. In any givencase, the amount of energy absorbed and stored by the spring armrelative to the amount of energy absorbed and dissipated by themechanical fuse means will depend upon the amount of fuse resistance.

In one embodiment, the spring arm is mechanically fused by an elongatedmechanical fuse strip comprising a central portion extending lengthwiseover the arm and a plurality of fuse tabs extending transversely outwardfrom the central portion to the base member. Each of the tabs is securedto the base member for providing fuse resistance to the flexing of thearm from the unflexed position to the flexed position.

Advantageously, the central portion of the fuse strip and the tabs areintegrally formed. Further, the central portion comprises opposedlongitudinally extending first and second sides connected by crosspiecesat spaced intervals. A first sub-plurality of the tabs extendstransversely outward from the first side of the central portion, and asecond sub-plurality of the tabs extends transversely outward from thesecond side of the central portion.

By directing the force of mechanical energy from an external source tothe distal end of the spring arm such that the arm is flexed from itsunflexed position to its flexed position, a part of the energy may bestored and another part dissipated.

The spring arm may be mechanically fused by other means, for example, bya plurality of shear pins secured at spaced intervals along the basemember, each fuse extending over the arm for providing fuse resistanceto the flexing of the arm from the unflexed position to the flexedposition.

In some applications, it may be considered desirable to provide a stageof resistance beyond that offered by fuse resistance. Advantageously, afurther stage of resistance is provided a flexible strap formed fromseat belt or similar material. One end of the strap is connected to thebase member and an opposed end is connected to the spring arm. The straphas a length sized to limit the arm from flexing beyond a predeterminedmaximum flexed position.

Energy storage devices as described above may be used in a variety ofapplications. In one such application, the distal end of the spring armis adapted to carry an end of a passenger safety crossbar.

Accordingly, and in another aspect of the present invention, there isprovided a system for protecting a passenger seated in a vehicle on avehicle seat, the system comprising a passenger safety crossbarextending between opposed ends with each end being carried by the distalend of the spring arm of an energy absorption device as described above.In the present context, each energy absorption device may be referred toas a crossbar support. In practice, the spring arm and the crossbarinclude suitable padding.

The base member of each such crossbar support extends upwardly andrearwardly from a lower end mounted in the vehicle forward of the seat.Preferably, the mounting of at least one of the supports is a pivotalmounting which permits movement of the crossbar from a closed positionprotecting a passenger while seated in the seat to an open positionpermitting passenger access to and egress from the seat.

In a preferred embodiment where one of the base members is pivotallymounted, the system includes means for releasably latching the basemembers to a frame member of the seat. Further, the crossbar is formedfrom a resilient material for springing the crossbar to its openposition when the base members is unlatched from the frame member.

The spring arm and fuse resistance provided by each crossbar support inthe foregoing system may be designed to absorb a predetermined amount ofenergy. If the supports include flexible straps (as is preferably thecase) to provide a further stage of resistance as described above then,in cases where the predetermined amount of energy is surpassed, furtherenergy will be dissipated when the straps reach their maximumextensions.

It will be noted that the spring arms and the crossbar effectively serveto compartmentalize a passenger in his or her seat both in the unflexedand flexed positions of the spring arms. The compartmentalization isenhanced by the resilience of the spring arms which will serve to urgethe arms toward their unflexed positions after deflection resulting fromthe impact of a passenger on the crossbar. Thus while a passenger willbear against the crossbar during a crash and may lift away from his orher seat as the crossbar moves with deflection of the spring arms, therewill be a return force which will assist to return the passenger to hisor her seat. The compartmentalization is enhanced by the flexible strapsbecause they not only provide a second stage of resistance, but can actas a flexible barrier in the case of side impacts and angled impacts.

The foregoing and other features and advantages of the present inventionwill now be described with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of the framework of a conventional benchseat on a bus and a passenger safety crossbar system, the systemincluding a crossbar and a pair of energy absorbing crossbar supports inaccordance with the present invention.

FIG. 2 is a side elevation view of the crossbar system illustrated inFIG. 1.

FIG. 3 is an isometric view as in FIG. 1, but showing the crossbar in anopen position.

FIG. 4 is a side elevation view of the crossbar system illustrated inFIG. 3.

FIG. 5 is a section view showing the crossbar support in FIG. 2 in moredetail.

FIG. 6 is an isometric view of one of the crossbar supports.

FIG. 7 is an end elevation view of the crossbar support shown in FIG. 6.

FIG. 8 is a top view of the crossbar support shown in FIG. 6.

FIG. 9 is a side elevation view of the crossbar support shown in FIG. 6.

FIG. 10 is a bottom view of the crossbar support shown in FIG. 6.

FIG. 11 is a top view of a mechanical fuse strip forming part of thecrossbar support shown in FIG. 6.

FIG. 12 is a side elevation view that representationally shows thecrossbar system in use during normal travel.

FIG. 13 is a side elevation view that representationally shows thecrossbar system in use at a moment shortly after a crash has occurred.

FIG. 14 is a side elevation view that representationally shown thecrossbar system in use at a subsequent moment after a crash hasoccurred.

FIG. 15 is an end view illustrating the natural, unstressed shape thecrossbar shown in FIGS. 1-5.

DETAILED DESCRIPTION

In FIG. 1, the framework of a bench seat generally designated 200 isshown together with a pair of energy absorbing crossbar supportsgenerally designated 20, 20 a. As well, FIG. 1 shows a portion of theframework of a similar bench seat generally designated 200 a positionedimmediately in front of seat 200. Conventional padding for seats 200,200 a is not shown in FIGS. 1-5. But, such padding is depicted in FIGS.12-14.

Typically, a bus (not shown) will include a number of seats such asseats 200, 200 a on one side of a passenger aisle, and a number ofadditional seats which are mirror images of seats 200, 200 a on theother side of the passenger aisle. All views in FIGS. 1-4 are from theaisle.

The framework for each seat 200, 200 a includes an outer side 205supported by a rail 300 which forms part of and extends along an innerwall of the bus. An inner side 210 of the framework is supported by apair of legs 215, 216 which include floor plates 217, 218 used to securethe legs to the floor of the bus. Further, the framework includes a sidearm structure 220, and an angular strut 230 positioned generally belowthe side arm structure.

As best seen in FIG. 5, crossbar support 20 includes an elongated basemember 22 extending upwardly and rearwardly from a lower end 23 mountedforward of seat 200 by means of a rod 80 which extends into a pivotconnection 82. Pivot connection 82 includes a pivot pin 83 which extendstransversely through rod 80, and a rod 85 which is threaded into abracket 231 at the upper end of strut 230 of seat 200 a. The threadedconnection between rod 85 and bracket 231 allows length adjustments tobe made so that support 20 can be precisely fitted between seats 200,200 a.

Crossbar support 20 also includes an elongated spring arm 30 extendinglongitudinally upwardly and rearwardly from a lower end 32 secured tothe base member to a distal end 34 which is adapted to carry an end of apassenger safety crossbar 10.

Arm 30 has resilience for storing mechanical energy. Thus, when arm 30is flexed from the normally unflexed position shown in FIG. 5 (viz.where arm 30 extends along base member 22) to a flexed position asindicated by broken line 100 (viz. where arm 30 bends in an arc awayfrom base member 22), there is a resilient force tending to return thearm to its unflexed position.

As described below in more detail, crossbar support 20 further includesa plurality of mechanical fuses 40 to provide mechanical fuse resistanceto flexing of arm 30. When the arm 30 flexed to the position indicatedby line 100, the fuses will break or shear thereby absorbing anddissipating mechanical energy while arm 30 absorbs and stores mechanicalenergy.

Crossbar support 20 also includes a flexible strap 50 which is connectedat one end to base member 22 and at the other to spring arm 30. In FIG.5, strap 50 is compactly folded back and forth upon itself within basemember 22. However, as indicated by arrow 101, it will be drawnoutwardly with spring arm 30 when the arm flexes. When fully extended,the strap will limit further flexing of the arm.

In FIGS. 1, 2 and 5, crossbar support 20 is latched in a closedposition. To facilitate latching, one portion 60 of a conventionallatching mechanism is carried by segment 221 of side arm structure 220while a cooperating portion 61 is carried by crossbar support 20. Whenunlatched as shown in FIGS. 3 and 4, crossbar support 20 is heldupwardly and away from side arm structure 220 by crossbar 10. Thisallows passengers easy access to and egress from the seating areaprovided by seat 200. More particularly, and as best seen in FIG. 15,crossbar 10 is formed from a resilient material with a longitudinaltwist about its longitudinal axis 11. This is its normal, unstressedshape, and thus naturally holds crossbar support arm 20 in the openposition shown in FIGS. 2 and 4. To then move crossbar support 20 to itsclosed position, a passenger normally will pull rearwardly on crossbar10. As can be seen in FIGS. 1, 2 and 5, the longitudinal twist which isvisible in FIG. 15 is then absent. When crossbar support 20 issubsequently unlatched, the resilience of crossbar 10 lifts the supportback to its open position.

Referring to FIGS. 1 and 3, the structure of crossbar support 20 a issubstantially the same as that of crossbar support 20, its distal end 34a normally holding the end of crossbar 10 opposite to that normally heldby distal end 34 of support 20. The lower end of support 20 a ispivotally carried by a pivot connection 82 a substantially the same aspivot connection 82. Pivot connection 82 a includes a rod 85 a which isthreaded into bracket 88 mounted on rail 300, the latter of which is anormal part of a conventional school bus (not shown). The upper end ofsupport 20 a is held by a brace 89 such that support 20 a extendssubstantially parallel to support 20.

FIGS. 6 to 11 illustrate aspects of crossbar support 20 in more detail.The support 20 includes an elongated mechanical fuse strip 40 whichextends over spring arm 30, and which is integrally formed from thinsheet steel. Strip 40 comprises a central portion having opposedlongitudinally extending sides 41, 42 connected at spaced intervals bycrosspieces 43, a first plurality of fuse tabs 44 extending transverselyoutward from side 41, and a second plurality of fuse tabs 45 extendingtransversely outward from side 42. All of the tabs are secured in slots25 on opposed sides of base member 22. When spring arm 30 is flexed, itbears against the tabs and when flexed to a sufficient degree will breakor shear the tabs thereby absorbing and dissipating mechanical energy.

As indicated above, a crossbar support may be mechanically fused bymeans other than the mechanical fuse strip that has been described. Forexample, with incidental structural modifications that will be readilyapparent to those skilled in the art, individual shear pins could begenerally positioned where each crosspiece 43 is positioned as shown inFIG. 3, and would serve to resist flexing of a spring arm such as springarm 30. However, a potential disadvantage of shear pins is that whenthey do break shear they may leave ragged edges which in themselves mayprovide a heightened risk of injury in the circumstances of a crash.

With a crash test dummy serving as a passenger 400, FIGS. 12 to 14illustrate the use of the present invention in a representative manner.In FIG. 12, the situation is one of normal travel. Passenger 400 isseated rearwardly away from crossbar 10 which is carried by crossbarsupport 20. FIG. 13 depicts the situation at an early moment after acollision has occurred. Passenger 400 has been propelled forward and hasimpacted on crossbar 20. In response, the spring arm in support 20 hasbegun to flex. Crossbar 10 has moved slightly forwardly and upwardly inrelation to seat 200. Subsequently, in FIG. 14, the momentum ofpassenger 400 has forced the spring arm of support 20 to a fully flexedposition where further flexing is restrained by strap 50. With furtherreference to FIG. 14, it will be understood that when the forwardmomentum of the passenger 400 has ended then the stored energy in springarm 30 will urge the passenger back towards seat 200. At all timescrossbar support 20 has remained latched in its closed position.

Various modifications and changes to the embodiment that has beendescribed can be made without departing from the scope of the presentinvention, and will undoubtedly occur to those skilled in the art. Theinvention is not to be construed as limited to the particular embodimentthat has been described and should be understood as encompassing allthose embodiments which are within the spirit and scope of the claimsthat follow.

1. An energy absorption device; comprising: (a) an elongated basemember; (b) an elongated spring arm extending longitudinally from afirst end secured to said base member to a distal end; said arm havingresilience for storing mechanical energy when flexed from a normallyunflexed position where said distal end is relatively near said basemember to a flexed position where said distal end is relatively far fromsaid base member; and (c) mechanical fuse means for providing fuseresistance to the flexing of said arm from said unflexed position tosaid flexed position.
 2. An energy absorption device; comprising: (a) anelongated base member; (b) an elongated spring arm extendinglongitudinally from a first end secured to said base member to a distalend; said arm having resilience for storing mechanical energy whenflexed from a normally unflexed position where said distal end isrelatively near said base member to a flexed position where said distalend is relatively far from said base member; and (c) a plurality ofmechanical fuses secured at spaced intervals along said base member,each fuse extending over said arm for providing fuse resistance to theflexing of said arm from said unflexed position to said flexed position.3. A device as defined in claim 2, where each of said fuses is a shearpin.
 4. An energy absorption device; comprising: (a) an elongated basemember; (b) an elongated spring arm extending longitudinally from afirst end secured to said base member to a distal end; said arm havingresilience for storing mechanical energy when flexed from a normallyunflexed position where said distal end is relatively near said basemember to a flexed position where said distal end is relatively far fromsaid base member; and (c) an elongated mechanical fuse strip comprisinga central portion extending lengthwise over said arm and a plurality offuse tabs extending transversely outward from said central portion tosaid base member, each of said tabs being secured to said base memberfor providing fuse resistance to the flexing of said arm from saidunflexed position to said flexed position.
 5. A device as defined inclaim 4, wherein said central portion of said strip and said tabs areintegrally formed.
 6. A device as defined in claim 5, wherein: (a) saidcentral portion comprises opposed longitudinally extending first andsecond sides connected by crosspieces at spaced intervals; and (b) afirst sub-plurality of said tabs extends transversely outward from saidfirst side of said central portion, and a second sub-plurality of saidtabs extends transversely outward from said second side of said centralportion.
 7. A device as defined in claim 1, wherein said distal end ofsaid arm is adapted to carry an end of a passenger safety crossbar.
 8. Adevice as defined in claim 1, further including a flexible strapconnected at one end to said base member and at an opposed end to saidarm, said strap having a length sized to limit said arm from flexingbeyond a predetermined maximum flexed position.
 9. A system forprotecting a passenger seated in a vehicle on a vehicle seat, saidsystem comprising a passenger safety crossbar extending between opposedends, each of said ends being carried by an associated crossbar support,each of said crossbar supports comprising: (a) an elongated base memberextending upwardly and rearwardly from a lower end mounted in saidvehicle forward of said seat; (b) an elongated spring arm extendinglongitudinally upwardly and rearwardly from a lower end secured to saidbase member to a distal end; the associated end of said crossbar beingsecured to said distal end, said arm having resilience for storingmechanical energy when flexed from a normally unflexed position wheresaid distal end is relatively near said base member to a flexed positionwhere said distal end is relatively far from said base member; and (c)mechanical fuse means for providing fuse resistance to the flexing ofsaid arm from said unflexed position to said flexed position.
 10. Asystem for protecting a passenger seated in a vehicle on a vehicle seat,said system comprising a passenger safety crossbar extending betweenopposed ends, each of said ends being carried by an associated crossbarsupport, each of said crossbar supports comprising: (a) an elongatedbase member extending upwardly and rearwardly from a lower end mountedin said vehicle forward of said seat; (b) an elongated spring armextending longitudinally upwardly and rearwardly from a lower endsecured to said base member to a distal end; the associated end of saidcrossbar being secured to said distal end, said arm having resiliencefor storing mechanical energy when flexed from a normally unflexedposition where said distal end is relatively near said base member to aflexed position where said distal end is relatively far from said basemember; and (c) a plurality of mechanical fuses secured at spacedintervals along said base member, each fuse extending over said arm forproviding fuse resistance to the flexing of said arm from said unflexedposition to said flexed position.
 11. A system as defined in claim 10,where each of said fuses is a shear pin.
 12. A system for protecting apassenger seated in a vehicle on a vehicle seat, said system comprisinga passenger safety crossbar extending between opposed ends, each of saidends being carried by an associated crossbar support, each of saidcrossbar supports comprising: (a) an elongated base member extendingupwardly and rearwardly from a lower end mounted in said vehicle forwardof said seat; (b) an elongated spring arm extending longitudinallyupwardly and rearwardly from a lower end secured to said base member toa distal end; the associated end of said crossbar being secured to saiddistal end, said arm having resilience for storing mechanical energywhen flexed from a normally unflexed position where said distal end isrelatively near said base member to a flexed position where said distalend is relatively far from said base member; and (c) an elongatedmechanical fuse strip comprising a central portion extending lengthwiseover said arm and a plurality of fuse tabs extending transverselyoutward from said central position to said base member, each of saidtabs being secured to said base member for providing fuse resistance tothe flexing of said arm from said unflexed position to said flexedposition.
 13. A system as defined in claim 12, wherein said centralportion of said strip and said tabs are integrally formed.
 14. A systemas defined in claim 13, wherein: (a) said central portion comprisesopposed longitudinally extending first and second sides connected bycrosspieces at spaced intervals; and (b) a first sub-plurality of saidtabs extends transversely outward from said first side of said centralportion, and a second sub-plurality of said tabs extends traverselyoutwardly from said second side if said central portion.
 15. A system asdefined in claim 9, each of said crossbar supports further including anassociated flexible strap connected at one end to the base member of theassociated crossbar support and at an opposed end to the arm of theassociated crossbar support, said strap having a length sized to limitthe arm of the associated crossbar support from flexing beyond apredetermined maximum flexed position.
 16. A system as defined in claim9, wherein said lower end of at least one of said base members ispivotally mounted in said vehicle to permit movement of said crossbarfrom a closed position protecting a passenger while seated in said seatto an open position permitting passenger access to and egress from saidseat.
 17. A system as defined in claim 9, wherein: (a) said lower end ofone of said base members is pivotally mounted in said vehicle to permitmovement of said crossbar from a closed position protecting a passengerwhile seated in said seat to an open position permitting passengeraccess to and egress from said seat; (b) said system further includingmeans for releasably latching said one of said base members to a framemember of said seat.
 18. A system as defined in claim 17, wherein saidcrossbar is formed from a resilient material for springing said crossbarto said open position when said one of said base members is unlatchedfrom said frame member.